From dc75456b24f0637fe6452488a2da1b872c3d5f4c Mon Sep 17 00:00:00 2001
From: ArtificialPB <matej@kriptal.io>
Date: Wed, 11 Dec 2024 15:18:29 +0100
Subject: [PATCH] feat(signers): add support for creating random
 `PrivateKeySigner`

additionally, re-use cached SecureRandom instance
---
 .../src/main/kotlin/io/ethers/crypto/Hashing.kt       | 10 ++++++++++
 .../kotlin/io/ethers/crypto/bip39/MnemonicCode.kt     |  7 +++----
 .../main/kotlin/io/ethers/signers/PrivateKeySigner.kt | 11 +++++++++++
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/ethers-crypto/src/main/kotlin/io/ethers/crypto/Hashing.kt b/ethers-crypto/src/main/kotlin/io/ethers/crypto/Hashing.kt
index d3a5dbc2..9ccca7ec 100644
--- a/ethers-crypto/src/main/kotlin/io/ethers/crypto/Hashing.kt
+++ b/ethers-crypto/src/main/kotlin/io/ethers/crypto/Hashing.kt
@@ -6,10 +6,20 @@ import org.bouncycastle.crypto.macs.HMac
 import org.bouncycastle.crypto.params.KeyParameter
 import org.bouncycastle.jcajce.provider.digest.Keccak
 import org.bouncycastle.jcajce.provider.digest.SHA256
+import java.security.SecureRandom
 
 object Hashing {
     private val MESSAGE_PREFIX = "\u0019Ethereum Signed Message:\n".toByteArray()
     private const val VERSIONED_HASH_VERSION_KZG = 0x01.toByte()
+    private val secureRandom by lazy { SecureRandom() }
+
+    /**
+     * Get cached [SecureRandom] instance. Instance is created on first access.
+     * */
+    @JvmStatic
+    fun secureRandom(): SecureRandom {
+        return secureRandom
+    }
 
     /**
      * Construct and hash [message] based on [EIP-191](https://eips.ethereum.org/EIPS/eip-191) standard (version 0x01).
diff --git a/ethers-crypto/src/main/kotlin/io/ethers/crypto/bip39/MnemonicCode.kt b/ethers-crypto/src/main/kotlin/io/ethers/crypto/bip39/MnemonicCode.kt
index b6d2f9cb..789dacc6 100644
--- a/ethers-crypto/src/main/kotlin/io/ethers/crypto/bip39/MnemonicCode.kt
+++ b/ethers-crypto/src/main/kotlin/io/ethers/crypto/bip39/MnemonicCode.kt
@@ -1,11 +1,11 @@
 package io.ethers.crypto.bip39
 
+import io.ethers.crypto.Hashing
 import org.bouncycastle.crypto.digests.SHA512Digest
 import org.bouncycastle.crypto.generators.PKCS5S2ParametersGenerator
 import org.bouncycastle.crypto.params.KeyParameter
 import org.bouncycastle.jcajce.provider.digest.SHA256
 import java.nio.charset.StandardCharsets
-import java.security.SecureRandom
 import java.util.Collections
 
 /**
@@ -130,7 +130,7 @@ class MnemonicCode @JvmOverloads constructor(
         private const val SEED_ITERATIONS = 2048
 
         /**
-         * Create a new mnemonic code from random entropy, using [SecureRandom].
+         * Create a new mnemonic code from random entropy, using [Hashing.secureRandom].
          * */
         @JvmStatic
         @JvmOverloads
@@ -138,9 +138,8 @@ class MnemonicCode @JvmOverloads constructor(
             bitsOfEntropy: Int = 256,
             wordList: MnemonicWordList = MnemonicWordListEnglish,
         ): MnemonicCode {
-            val rand = SecureRandom()
             val entropy = ByteArray(bitsOfEntropy / 8)
-            rand.nextBytes(entropy)
+            Hashing.secureRandom().nextBytes(entropy)
 
             return fromEntropy(entropy, wordList)
         }
diff --git a/ethers-signers/src/main/kotlin/io/ethers/signers/PrivateKeySigner.kt b/ethers-signers/src/main/kotlin/io/ethers/signers/PrivateKeySigner.kt
index c1e84d8f..2e7d4a18 100644
--- a/ethers-signers/src/main/kotlin/io/ethers/signers/PrivateKeySigner.kt
+++ b/ethers-signers/src/main/kotlin/io/ethers/signers/PrivateKeySigner.kt
@@ -4,6 +4,7 @@ import io.ethers.core.FastHex
 import io.ethers.core.types.Address
 import io.ethers.core.types.Bytes
 import io.ethers.core.types.Signature
+import io.ethers.crypto.Hashing
 import io.ethers.crypto.Secp256k1
 
 /**
@@ -59,5 +60,15 @@ class PrivateKeySigner(val signingKey: Secp256k1.SigningKey) : Signer {
 
             return Secp256k1.SigningKey(bytes)
         }
+
+        /**
+         * Create a new [PrivateKeySigner] from random entropy, using [Hashing.secureRandom].
+         * */
+        @JvmStatic
+        fun random(): PrivateKeySigner {
+            val privateKey = ByteArray(32)
+            Hashing.secureRandom().nextBytes(privateKey)
+            return PrivateKeySigner(privateKey)
+        }
     }
 }